CAROTENOIDS 



Samples taken of Russian marsh sapropels^' were richer in caro- 

 tenoids than were samples taken from Muscovite lakes. - * The super- 

 ficial layers of the lake muds carried the highest concentration of caro- 

 tenoids, w^hich amounted, on the average, to 1-67 mg./g. and 2-62 

 mg./g. of carotenes and xanthophylls respectively. ^ * Karrer and 

 Koenig2 5 found that rhodoviolascin was by far the predominating 

 pigment in a red mud obtained from Kenya. Van NieH^ considers 

 that this is due to the fact that the material was a natural mass-culture 

 of the purple sulphur-containing bacteria. 



Beattie ^ • examined the detritus in caves in North Italy and found 

 that carotenoids are associated with underground rivers, for large 

 quantities were found in the mud of a pool fed by the river whilst none 

 was found in mud in a drip pool unconnected with the river. Air- 

 borne detritus from the mouth of the cave and similar material from 

 Chislehurst contained little or no pigment. As in the case of Baudisch 

 and von Euler's'*'^ " littoralgyttja," xanthophylls predominate in the 

 river-borne detritus. 



Amphibia 



As early as 1882 Kiihne - ' found evidence for the presence of caro- 

 tenoids in the skin of the following species of frogs and toads : Hyla 

 arborea, Rana esculenta, Bufo viridis, B. calamita, and B. vulgaris. 

 This was confirmed qualitatively for R. esculenta by Kruckenberg^ 

 and R. esculenta and R. temporaria by Lonnberg. ^ s Dietel ^ » found 

 carotene in the liver and ovaries of R. temporaria, and van Eekelen ^ " 

 carotene and xanthophyllic esters in the skins of both R. esculenta and 

 R. temporaria. Manunta, ^ i studying R. esculenta and H. arborea, 

 found large amounts of carotene and small amounts of free xantho- 

 phylls in the former and equal amounts of carotenes and esterified 

 xanthophylls in the latter. 



It was Rand, ' ^ however, who first demonstrated that the frog was a 

 veritable living storehouse of carotenoids for they occur in skin, liver, 

 kidney, lungs, ovaries, ova, oviducts, testes, and fat bodies of both 

 summer and winter frogs. This was later confirmed by Brunner and 

 Stein 3^ by Zechmeister and Tuzson, '* and Morton and Rosen. ^^ 

 Zechmeister and Tuzson identified a- and ^-carotene, lutein (xantho- 

 phyll), and zeaxanthin and Morton and Rosen, whilst confirming this 

 work, also found evidence for the presence of mono- and di-xantho- 

 phyllic esters. Lutein (xanthophyll) has also been detected in the frogs 

 retinae ^ ^ where it may exist as a protein complex, a «a, 3 ? Lutein (xan- 

 thophyll) is also present in the pigment epithelium of the eyes of the 

 bullfrog Rana catesbiana^^ and the edible frog R. esculenta J '^^ 



210 



